Drought alters interactions between root and foliar herbivores

Drought can alter plant quality and the strength of trophic interactions between herbivore groups, and is likely to increase in occurrence and severity under climate change. We hypothesized that changes in plant chemistry due to root herbivory and drought stress would affect the performance of a generalist and a specialist aphid species feeding on a Brassica plant. High drought stress increased the negative effect of root herbivory on the performance of both aphid species (30 % decrease in fecundity and 15 % reduction in intrinsic rate of increase). Aphid performance was greatest at moderate drought stress, though the two species differed in which treatment combination maximized performance. Nitrogen concentration was greatest in high and moderately drought-stressed plants without root herbivores and moderately drought-stressed plants under low root herbivore density, and correlated positively with aphid fecundity for both species. Glucosinolate concentrations increased 62 % under combined drought stress and root herbivory, and were positively correlated with extended aphid development time. Root herbivory did not influence relative water content and foliar biomass under normal water regimes but they decreased 24 and 63 %, respectively, under high drought stress. This study shows that drought can alter the strength of interactions between foliar and root herbivores, and that plant chemistry is key in mediating such interactions. The two aphid species responded in a broadly similar way to root herbivore and drought-stress treatments, which suggests that generalized predictions of the effects of abiotic factors on interactions between above- and below-ground species may be possible.     

Impact of foliar herbivory on the development of a root-feeding insect and its parasitoid

The majority of studies exploring interactions between above- and below-ground biota have been focused on the effects of root-associated organisms on foliar herbivorous insects. This study examined the effects of foliar herbivory by Pieris brassicae L. (Lepidoptera: Pieridae) on the performance of the root herbivore Delia radicum L. (Diptera: Anthomyiidae) and its parasitoid Trybliographa rapae (Westwood) (Hymenoptera: Figitidae), mediated through a shared host plant Brassica nigra L. (Brassicaceae). In the presence of foliar herbivory, the survival of D. radicum and T. rapae decreased significantly by more than 50%. In addition, newly emerged adults of both root herbivores and parasitoids were significantly smaller on plants that had been exposed to foliar herbivory than on control plants. To determine what factor(s) may have accounted for the observed results, we examined the effects of foliar herbivory on root quantity and quality. No significant differences in root biomass were found between plants with and without shoot herbivore damage. Moreover, concentrations of nitrogen in root tissues were also unaffected by shoot damage by P. brassicae larvae. However, higher levels of indole glucosinolates were measured in roots of plants exposed to foliar herbivory, suggesting that the development of the root herbivore and its parasitoid may be, at least partly, negatively affected by increased levels of these allelochemicals in root tissues. Our results show that foliar herbivores can affect the development not only of root-feeding insects but also their natural enemies. We argue that such indirect interactions between above- and below-ground biota may play an important role in the structuring and functioning of communities.     

Parasitoids select plants more heavily infested with their caterpillar hosts: a new approach to aid interpretation of plant headspace volatiles

Plants produce volatile organic compounds (VOCs) in response to herbivore attack, and these VOCs can be used by parasitoids of the herbivore as host location cues. We investigated the behavioural responses of the parasitoid Cotesia vestalis to VOCs from a plant-herbivore complex consisting of cabbage plants (Brassica oleracea) and the parasitoids host caterpillar, Plutella xylostella. A Y-tube olfactometer was used to compare the parasitoids' responses to VOCs produced as a result of different levels of attack by the caterpillar and equivalent levels of mechanical damage. Headspace VOC production by these plant treatments was examined using gas chromatography-mass spectrometry. Cotesia vestalis were able to exploit quantitative and qualitative differences in volatile emissions, from the plant-herbivore complex, produced as a result of different numbers of herbivores feeding. Cotesia vestalis showed a preference for plants with more herbivores and herbivore damage, but did not distinguish between different levels of mechanical damage. Volatile profiles of plants with different levels of herbivores/herbivore damage could also be separated by canonical discriminant analyses. Analyses revealed a number of compounds whose emission increased significantly with herbivore load, and these VOCs may be particularly good indicators of herbivore number, as the parasitoid processes cues from its external environment.     

Plant population size and isolation affect herbivory of <Emphasis Type="Italic">Silene latifolia</Emphasis> by the specialist herbivore <Emphasis Type="Italic">Hadena bicruris</Emphasis> and parasitism of the herbivore by parasitoids

Habitat fragmentation can affect levels of herbivory in plant populations if plants and herbivores are differentially affected by fragmentation. Moreover, if herbivores are top–down controlled by predators or parasitoids, herbivory may also be affected by differential effects of fragmentation on herbivores and their natural enemies. We used natural Silene latifolia populations to examine the effects of plant population size and isolation on the level of herbivory by the seed predating noctuid Hadena bicruris and the rate of parasitism of the herbivore by its parasitoids. In addition, we examined oviposition rate, herbivory and parasitism in differently sized experimental populations. In natural populations, the level of herbivory increased and the rate of parasitism decreased with decreasing plant population size and increasing degree of isolation. The number of parasitoid species also declined with decreasing plant population size. In the experimental populations, the level of herbivory was also higher in smaller populations, in accordance with higher oviposition rates, but was not accompanied by lower rates of parasitism. Similarly, oviposition rate and herbivory, but not parasitism rate, increased near the edges of populations. These results suggests that in this system with the well dispersing herbivore H. bicruris, habitat fragmentation increases herbivory of the plant through a behavioural response of the moth that leads to higher oviposition rates in fragmented populations with a reduced population size, increased isolation and higher edge-to-interior ratio. Although the rate of parasitism and the number of parasitoid species declined with decreasing population size in the natural populations, we argue that in this system it is unlikely that this decline made a major contribution to increased herbivory.     

Organic and conventional fertilizer effects on a tritrophic interaction: parasitism,performance and preference of Cotesia vestalis

Interest in sustainable farming methods that rely on alternatives to conventional synthetic fertilizers and pesticides is increasing. Sustainable farming methods often utilize natural populations of predatory and parasitic species to control populations of herbivores, which may be potential pest species. We investigated the effects of several types of fertilizer, including those typical of sustainable and conventional farming systems, on the interaction between a herbivore and parasitoid. The effects of fertilizer type on percentage parasitism, parasitoid performance, parasitoid attack behaviour and responses to plant volatiles were examined using a model Brassica system, consisting of Brassica oleracea var capitata, Plutella xylostella (Lepidoptera) larvae and Cotesia vestalis (parasitoid). Percentage parasitism was greatest for P. xylostella larvae feeding on plants that had received either a synthetic ammonium nitrate fertilizer or were unfertilized, in comparison to those receiving a composite fertilizer containing hoof and horn. Parasitism was intermediate on plants fertilized with an organically produced animal manure. Male parasitoid tibia length showed the same pattern as percentage parasitism, an indication that offspring performance was maximized on the treatments preferred by female parasitoids for oviposition. Percentage parasitism and parasitoid size were not correlated with foliar nitrogen concentration. The parasitoids did not discriminate between hosts feeding on plants in the four fertilizer treatments in parasitoid behaviour assays, but showed a preference for unfertilized plants in olfactometer experiments. The percentage parasitism and tibia length results provide support for the preference–performance hypothesis.     

Response of the parasitoid Telenomus podisi to induced volatiles from soybean damaged by stink bug herbivory and oviposition

Abstract

Egg parasitoids have a short time frame in which their host eggs are suitable for parasitism, and in several systems these parasitoids respond to plant volatiles induced by oviposition on the plant (either in isolation or in combination with feeding damage) as a means of finding suitable hosts. It is known that the parasitoid of pentatomid eggs Telenomus podisi responds to damage done to soybeans by female Euschistus heros, its preferred host. In this study our aim was to determine the type of E. heros damage to soybean (herbivory, oviposition or a combination of both) necessary for attraction of T. podisi. In a Y-tube olfactometer the parasitoid has shown to respond to the undamaged plant over clean air and herbivory-damaged plants over undamaged plants. However, the parasitoids did not respond to the treatments where oviposition occurred, either in isolation or in combination with herbivory. Analysis of volatile blends revealed that herbivory plus oviposition damage to soybean induced a volatile blend different to those induced when herbivory or oviposition occurred separately. These results, along with other results from this system, suggest that T. podisi uses plant volatile cues associated with female E. heros damage in order to be present when E. heros lays its eggs, and thus ensure its resource is optimal for parasitism.     

Damage to sagebrush attracts predators but this does not reduce herbivory

Emissions of volatiles increase following herbivory from many plant species and volatiles may serve multiple functions. Herbivore‐induced volatiles attract predators and parasitoids of herbivores and are often assumed to benefit plants by facilitating top‐down control of herbivores; this benefit of induced emissions has been tested only a few times. Volatile compounds released by experimentally clipped sagebrush shoots have been shown to reduce levels of chewing damage experienced by other shoots on the same plant and on neighboring sagebrush plants. In this study, I asked whether experimental clipping attracted predators of herbivorous insects to sagebrush shoots. I also evaluated aphid populations and chewing damage on clipped and unclipped shoots and whether predators were likely to have caused differences in aphids and chewing damage. Shoots that had been clipped recruited more generalist predators, particularly coccinellids and Geocoris spp. in visual surveys conducted during two seasons. Clipping also caused increased numbers of parasitized aphids in one season. Ants were common tending aphids but were not significantly affected by clipping. Despite the increase in generalist predators, clipped plants were more likely to support populations of aphids that increased during both seasons compared to aphids on unclipped control plants. Clipped shoots suffered less damage by chewing herbivores in the 1‐year in which this was measured. Chewing damage was not correlated with numbers of predators. These results suggest that predators and parasitoids were attracted to experimentally clipped sagebrush plants but that these predators were not effective at reducing net damage to the plant. This conclusion is not surprising as much of the herbivory is inflicted by grasshoppers and deer, herbivores that are not vulnerable to the predators attracted to sagebrush volatiles. More generally, it should not be assumed that predators that are attracted by herbivore‐induced volatiles necessarily benefit the plant without testing this hypothesis under field conditions.     

Estimation of hymenopteran parasitism in cereal aphids by using molecular markers

Polymerase chain reaction (PCR) primers were designed and tested for identification of immature parasitoids in small grain cereal aphids and for estimation of parasitism rates. PCR technique was evaluated for 1) greenhouse-reared greenbugs, Schizaphis graminum (Rondani), parasitized by Lysiphlebus testaceipes Cresson and 2) aphids collected from winter wheat fields in Caddo County, Oklahoma. For greenhouse samples, parasitism frequencies for greenbugs examined by PCR at 0, 24, and 48 h after removal of L. testaceipes parasitoids were compared with parasitism frequencies as determined by greenbug dissection. PCR was unable to detect parasitism in greenbugs at 0 and 24 h postparasitism, but it was able to detect parasitoids 48 h after parasitoid removal at frequencies that were not significantly different from dissected samples. Field-collected samples were analyzed by rearing 25 aphids from each sample and by comparing parasitoid frequencies of mummies developed and PCR performed on another 50 aphids. Aphid samples included corn leaf aphids, Rhopalosiphum maidis (Fitch); bird cherry-oat aphids, Rhopalosiphum padi (L.); English grain aphids, Sitobion avenae (F.); and greenbugs. Mummies were isolated until adult emergence, whereupon each parasitoid was identified to species (L. testaceipes was the only parasitoid species found). Parasitism detection frequencies for PCR also were not statistically different from parasitism frequencies of reared aphids. These results indicate that PCR is a useful tool for providing accurate estimates of parasitism rates and especially for identification of immature parasitoids to species.     

Trophic cascades initiated by fungal plant endosymbionts impair reproductive performance of parasitoids in the second generation

Variation in plant quality can transmit up the food chain and may affect herbivores and their antagonists in the same direction. Fungal endosymbionts of grasses change the resource quality by producing toxins. We used an aphid-parasitoid model system to explore how endophyte effects cascade up the food chain and influence individual parasitoid performance. We show that the presence of an endophyte in the grass Lolium perenne has a much stronger negative impact on the performance of the parasitoid Aphidius ervi than on its aphid host Metopolophium festucae. Although the presence of endophytes did not influence the parasitism rate of endophyte-naïve parasitoids or their offspring’s survival to adulthood, most parasitoids developing within aphids from endophyte-infected plants did not reproduce at all. This indicates a delayed but very strong effect of endophytes on parasitoid performance, which should ultimately affect plant performance negatively by releasing endophyte-tolerant herbivores from top-down limitations.     

Simultaneous feeding by aboveground and belowground herbivores attenuates plant-mediated attraction of their respective natural enemies

Herbivore-damaged plants emit volatile organic compounds that attract natural enemies of the herbivores. This form of indirect plant defence occurs aboveground as well as belowground, but it remains unclear how simultaneous feeding by different herbivores attacking leaves and roots may affect the production of the respective defence signals. We employed a setup that combines trapping of volatile organic signals and simultaneous measurements of the attractiveness of these signals to above and belowground natural enemies. Young maize plants were infested with either the foliar herbivore Spodoptera littoralis , the root herbivore Diabrotica virgifera virgifera , or with both these important pest insects. The parasitic wasp Cotesia marginiventris and the entomopathogenic nematode Heterorhabditis megidis were strongly attracted if their respective host was feeding on a plant, but this attraction was significantly reduced if both herbivores were on a plant. The emission of the principal root attractant was indeed reduced due to double infestation, but this was not evident for the leaf volatiles. The parasitoid showed an ability to learn the differences in odour emissions and increased its response to the odour of a doubly infested plant after experiencing this odour during an encounter with hosts. This first study to measure effects of belowground herbivory on aboveground tritrophic signalling and vice-versa reemphasizes the important role of plants in bridging interactions between spatially distinct components of the ecosystem.     

Genetic variation in plant below-ground response to elevated CO2 and two herbivore species

Aims

It is unclear how changing atmospheric conditions, including rising carbon dioxide concentration, influence interactions between above and below-ground systems and if intraspecific variation exists in this response.

Methods

We assessed interactive effects of atmospheric CO₂ concentration, above-ground herbivory, and plant genotype on root traits and mycorrhizal associations. Plants from five families of Asclepias syriaca, a perennial forb, were grown under ambient and elevated atmospheric CO₂ concentrations. Foliar herbivory by either lepidopteran caterpillars or phloem-feeding aphids was imposed. Mycorrhizal colonization, below-ground biomass, root biomass, and secondary defensive chemistry in roots were quantified.

Results

We observed substantial genetic variation among A. syriaca families in their mycorrhizal colonization levels in response to elevated CO₂ and herbivory treatments. Elevated CO₂ treatment increased root biomass in all genetic families, whereas foliar herbivory tended to decrease root biomass. Root cardenolide concentration and composition varied greatly among plant families, and elevated CO₂ treatment increased root cardenolides in two of the five plant families. Moreover, herbivores differentially affected the composition of cardenolides expressed below ground.

Conclusions

Increased atmospheric CO₂ has the potential to influence interactions among plants, herbivores and mycorrhizal fungi and intraspecific variation suggests that such interactions can evolve.     

Host‐searching responses to herbivory‐associated chemical information and patch use depend on mating status of female solitary parasitoid wasps

1. In a tritrophic interaction system consisting of plants, herbivores, and their parasitoids, chemicals released from plants after herbivory are known to play important roles for many female parasitoids to find their hosts efficiently. On the plant side, chemical information associated with herbivory can act as an indirect defence by attracting the natural enemies of the host herbivores. 2. However, mated and virgin females of haplodiploid parasitoids might not necessarily respond to such chemical cues in the same way. Since virgin females can produce only sons, they might refrain from searching for hosts to invest eggs until copulation, in order to produce both sexes. 3. Here, we investigated differential host‐searching behaviours shown by mated and virgin females in the solitary parasitoid wasp, Cotesia vestalis, in response to herbivory‐associated chemical information from cruciferous plants infested by their host larvae, Plutella xylostella. 4. Mated females showed a significantly higher flight preference for host‐infested plants over intact plants, while no preference was observed with virgin females. Mated females also showed more intensive antennal searching and ovipositor probing behaviours to leaf squares with wounds caused by hosts than did virgin females. Furthermore, mated females stayed longer in host patches with higher parasitism rates than virgin females. 5. These results indicate that mating status of C. vestalis females clearly influences their host‐searching behaviour in response to herbivory‐associated chemical information and patch exploitation. Female parasitoids seem to forage for hosts depending on their own physiological condition in a tritrophic system.     

Effect of belowground herbivory on parasitoid associative learning of plant odours

Root herbivores can influence both the performance and the behaviour of parasitoids of aboveground insect herbivores through changes in aboveground plant quality and in the composition of the plant's odour blend. Here we show that root herbivory by Delia radicum larvae did not influence the innate preferences for plant odours of the two closely related parasitoid species Cotesia glomerata and C. rubecula, but did affect their learned preferences, and did so in an opposite direction. While C. glomerata learned to prefer the odour of plants with intact roots, C. rubecula learned to prefer the odour of root‐infested plants. The learned preference of C. glomerata for the odour of plants with intact roots matches our previously published result of its better performance when developing in P. brassicae hosts feeding on this plant type. In contrast, the relatively stronger learned preference of C. rubecula for the odour of root‐infested plants cannot be merely explained by its performance, as the results of our present study indicate that D. radicum root herbivory did not influence the performance of C. rubecula nor of its host P. rapae. Our results stress the importance of assessing the influence of root herbivores on both innate and learned responses of parasitoids to plant odours.     

Hyperparasitoids Use Herbivore-Induced Plant Volatiles to Locate Their Parasitoid Host

Plants respond to herbivory with the emission of induced plant volatiles. These volatiles may attract parasitic wasps (parasitoids) that attack the herbivores. Although in this sense the emission of volatiles has been hypothesized to be beneficial to the plant, it is still debated whether this is also the case under natural conditions because other organisms such as herbivores also respond to the emitted volatiles. One important group of organisms, the enemies of parasitoids, hyperparasitoids, has not been included in this debate because little is known about their foraging behaviour. Here, we address whether hyperparasitoids use herbivore-induced plant volatiles to locate their host. We show that hyperparasitoids find their victims through herbivore-induced plant volatiles emitted in response to attack by caterpillars that in turn had been parasitized by primary parasitoids. Moreover, only one of two species of parasitoids affected herbivore-induced plant volatiles resulting in the attraction of more hyperparasitoids than volatiles from plants damaged by healthy caterpillars. This resulted in higher levels of hyperparasitism of the parasitoid that indirectly gave away its presence through its effect on plant odours induced by its caterpillar host. Here, we provide evidence for a role of compounds in the oral secretion of parasitized caterpillars that induce these changes in plant volatile emission. Our results demonstrate that the effects of herbivore-induced plant volatiles should be placed in a community-wide perspective that includes species in the fourth trophic level to improve our understanding of the ecological functions of volatile release by plants. Furthermore, these findings suggest that the impact of species in the fourth trophic level should also be considered when developing Integrated Pest Management strategies aimed at optimizing the control of insect pests using parasitoids.     

The effect of parasitism by Aphelinus abdominalis and drought on the walking movement of aphids

The effect of simulated plant stress and parasitism by Aphelinus abdominalis (Dalman) on the mobility of four species of aphids was investigated. The aphids were placed on water stressed potted plants or on excised leaf segments on dry or moist filter-paper in Petri dishes. Winter wheat (Triticum aestivum) was infested with Metopolophium dirhodum (Walker), Sitobion avenae (F.) and Rhopalosiphum padi (L.) (segments only), aubergine (Solanum melongena) leaf segments with Macrosiphum euphorbiae (Thomas). The aphids that moved off the plants were removed and their development stage determined at 24-h (drought-stressed plants) or 3-h (leaf segments) intervals. On intact plants, aphid larvae were reluctant to move, and only moved after moulting into adults. On cut leaves, young 1st and 2nd instar larvae were more reluctant to move than 3rd and 4th instar larvae and adults. The numbers moving were initially positively correlated with aphid population density, and in M. euphorbiae occurred mainly during the night. Depending on aphid species and parasitoid age, parasitism by A. abdominalis retarded or accelerated movement, but the differences between young and old larvae and adults persisted after parasitism. A. abdominalis lays male eggs in small hosts and female eggs in large hosts. Consequently, its sex ratio was affected by differential movement of the host aphids of the male and female parasitoids. Old larvae and adult aphids readily moved and carried off female parasitoids, while the small aphids were more likely to remain and give rise to male-biased sex ratios.     

Effects of decomposers and herbivores on plant performance and aboveground plant-insect interactions

Most ecologists acknowledge that plants are subject to complex interactions between both below- and aboveground dwelling animals. However, these complex interactions are seldomly investigated simultaneously. In a factorial common garden experiment we tested single and combined effects of decomposers, root herbivores and leaf herbivores on the growth, flower visitation, and abundance of naturally colonizing aphids and parasitoids on wild mustard ( Sinapis arvensis ). We found that the individual presence of either root herbivores or decomposers resulted in increased aphid abundance, demonstrating that the same aboveground plant–insect interaction can be released by different belowground processes. Enhanced aphid densities caused higher numbers of parasitoids. Furthermore, decomposers increased plant growth and plant fitness (measured as the number of seeds produced), indicating that mustard may benefit from nutrients provided by decomposers, regardless whether plants are attacked by root herbivores or leaf herbivores, or both simultaneously. More flower visits were observed in plants attacked by root herbivores but without leaf herbivores than in plants with both herbivores, suggesting that root herbivory can modify flower attractivity to pollinators. Our results suggest that patterns in plant–insect interactions above the ground are not only affected by aboveground factors but also by a wealth of different belowground processes mediated by the plant.     

Minor effects of two elicitors of insect and pathogen resistance on volatile emissions and parasitism of Spodoptera frugiperda in Mexican maize fields

Synthetic elicitors can be used to induce resistance in plants against pathogens and arthropod herbivores. Such compounds may also change the emission of herbivore-induced plant volatiles, which serve as important cues for parasitic wasps to locate their hosts. Therefore, the use of elicitors in the field may affect biological control of insect pests. To test this, we treated maize seedlings growing in a subtropical field in Mexico with methyl jasmonate (MeJA), an elicitor of defense responses against many insects, and benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH), an elicitor of resistance against certain pathogens. Volatile emission, herbivore infestation, pathogen infection, and plant performance (growth and grain yield) of treated and untreated maize plants were measured. Application of BTH slightly reduced volatile emission in maize, while MeJA increased the emission compared to control treatments. Despite the apparent changes in volatile emissions, the elicitor application did not consistently affect infestation by Spodoptera frugiperda larvae, the main insect pest found on the maize seedlings, and had only marginal effects on parasitism rates. Similarly, there were no treatment effects on infestation by other herbivores and pathogens. Results for the six replications that stretched over one summer and one winter season were highly variable, with parasitism rates and the species composition of the parasitoids differing significantly between seasons. This variability, as well as the severe biotic and abiotic stresses on young seedlings might explain why we measured only slight effects of elicitor application on pest incidence and biological control in this specific field study. Indeed, an additional field experiment under milder and more standardized conditions revealed that BTH induced significant resistance against Bipolaris maydis, a major pathogen in the experimental maize fields. Similar affects can be expected for herbivory and parasitism rates.     

Sources of variation in plant responses to belowground insect herbivory: a meta-analysis

Growing interest in belowground herbivory and the remarkable diversity of the accumulated information on this topic inspired us to quantitatively explore the variation in the outcomes of individual studies. We conducted a meta-analysis of 85 experimental studies reporting the effects of root-feeding insect herbivores (36 species) on plants (75 species). On average, belowground herbivory led to a 36.3% loss of root biomass, which was accompanied by a reduction in aboveground growth (-16.3%), photosynthesis (-11.7%) and reproduction (-15.5%). The effects of root herbivory on aboveground plant characteristics were significant in agricultural and biological control studies, but not in studies of natural systems. Experiments conducted in controlled environments yielded larger effects on plants than field experiments, and infestation experiments resulted in more severe effects than removal studies employing natural levels of herbivory. Simulated root herbivory led to greater aboveground growth reductions than similar root loss imposed by insect feeding. External root chewers caused stronger detrimental effects than sap feeders or root borers; specialist herbivores imposed milder adverse effects on plants than generalists. Woody plants suffered from root herbivory more than herbaceous plants, although root loss was similar in these two groups. Evergreen woody plants responded to root herbivory more strongly than deciduous woody plants, and grasses suffered from root herbivory more than herbs. Environmental factors such as drought, poor nutrient supply, among-plant competition, and aboveground herbivory increased the adverse effects of root damage on plants in an additive manner. In general, plant tolerance to root herbivores is lower than tolerance to defoliating aboveground herbivores.     

Drought impacts on above–belowground interactions: Do effects differ between annual and perennial host species?

Root herbivores can have a positive or negative effect on the abundance and/or performance of foliar phytophages. In addition, abiotic factors such as drought can either strengthen or weaken this effect, depending on the system under investigation. One explanation for these varying responses lies in differences in the physiological response of host plants to drought and root herbivores. Here, the impacts of root phytophages on a leaf-mining species feeding on annual and perennial plant species (four Sonchus species) were compared. The responses of plants and leaf-miners to drought and root herbivore treatments were not related to whether the host plant was an annual or perennial. However, where root feeders did affect foliar phytophage performance, this occurred only under a drought treatment, demonstrating the potential for climate change to alter the outcome of plant-mediated interactions.